Isight Camera working time to time

Hi. It's months that my sight Camera was not working. After trying any kind of software attempt to restore it to normal working, I was thinking it was a hardware issue and left it like that, saying to myself that sooner or later i would have taken the macboook to a store for camera replacement.

But yesterday, suddenly, during a SKYPE conf call, where I obviously connected only wth voice, the CAMERA OPTION was ACTIVATED. I couldn't believe it, and I clicked the camera button: WORKING AGAIN! i had a video call with my friend for few minutes, very happy to see my camera back at work.

Today the dream is gone... camera is again not available on Skype, Photobooth and Facetime. "Camera not avialable".

Have you ever experienced somthng like this?

Thanks and regards

Luca